The invention relates to a directional control valve arrangement.
A directional control valve arrangement of this type is made known in DE 196 27 306 A1. It includes a manually-actuated directional control valve having a blocking valve and pressure-limiting valve in a consumer passage. The purpose of the blocking valve is to minimize a load reduction on the consumer side caused by leakage from the directional control valve. In the case of a line system that is connected to the consumer passage, the blocking valve, which performs a sealing function, can cause an impermissibly high pressure to occur in the line system and in the consumer passage if extraneous heat is applied, e.g. solar radiation or heat dissipated by machinery. The impermissibly high pressure can damage the directional control valve arrangement, the line system and valves connected thereto. The pressure-limiting valve situated in the consumer passage is used to reduce the impermissibly high pressure and therefore prevent it from forming.
The blocking valve and its precontrol are controlled open by a plunger. The plunger can be mechanically actuated in the control-open direction using a connecting member formed on a valve spool of the directional control valve. The consumer passage can be connected to an intermediate chamber via the blocking valve and the pressure-limiting valve, wherein a pressure-medium connection between the intermediate chamber and a tank chamber can be controlled using the valve spool of the directional control valve. In addition, the intermediate chamber is connected to the tank chamber via a throttled passage, wherein the throttled passage is the gap between the valve spool and a valve housing that accommodates the valve spool.
If the pressure is impermissibly high, the pressure-limiting valve opens, thereby allowing pressure medium to flow from the consumer passage to the intermediate passage and, from there, via the throttled passage to the tank chamber.
A further solution for reducing an impermissibly high pressure in a consumer line in the presence of a directional control valve arrangement is presented in data sheet RD 66 132-01-R1/03.Q7 published by the applicant. According to the aforementioned solution, a blocking valve is situated in the consumer passage, as is the case in the previous publication. To limit the impermissibly high pressure, a thermo pressure-limiting valve is provided in a separate bore of a valve spool of the directional control valve arrangement. When a certain impermissibly high pressure is reached, a pressure-medium connection between the consumer passage and a tank passage is controlled open by the thermo pressure-limiting valve.
The disadvantage of the above-mentioned directional control valve arrangements is that the pressure-limiting valves are cost-intensive components having a complex design, require that the impermissibly high pressure to be limited be adjusted, and require a great deal of installation space.